This invention is directed to a tuning fork quartz crystal vibrator having like configured in-phase electrodes formed on the opposed planar surfaces of the tines and electrodes formed on the side surfaces of the tines to electrically couple the electrodes on the respective surfaces of the tines together and, in particular, to a method for forming the electrodes on at least the lengthwise side surface of the tines by masking the opposed planar surfaces of the vibrator and sputtering thin film conductive electrodes on the side surfaces of the tines.
Heretofore, subminiaturized quartz crystal vibrators, having high frequencies of vibration, have been manufactured by photo-etching techniques to thereby reduce the costs of manufacturing the vibrator and, at the same time, increase the reliability thereof. Such photo-etching processes include the steps of forming a thin film of conductive material in the shape of the vibrator on a quartz crystal plate, the conductive material being selected to be resistant to the etchant utilized to cut the quartz crystal. Thereafter, a photo-resist in the shape of the electrode is formed on the respective conductive layers. Next, the shape of the tuning fork quartz crystal vibrator is formed by utilizing a suitable etchant, whereafter a further etchant is utilized to remove the portions of the conductive material and, thereby, define the electrodes on the opposed planar surfaces of the vibrator. Nevertheless, a less than completely satisfactory result, of this method of manufacturing, is that the quartz crystal vibrator formed thereby has a reduced equivalent capacitance. It is noted that a characteristic of oscillator circuits, having quartz crystal vibrators therein, is that the lower the equivalent capacitance, the smaller the range over which the oscillating frequency, produced by the oscillator circuit, can be varied. Accordingly, a quartz crystal vibrator construction and method for forming same, that permits an increase in the equivalent capacitance of the quartz crystal vibrator and, hence, a resulting increase in the range of frequencies over which an oscillator circuit including same can be tuned, is desired.